Patient, female, 65 years old, with cauda equina injury, underwent surgery after perfecting the related examination, and was left with a urinary catheter after surgery. On the second day of the indwelling urinary catheter, the patient was found to be leaking urine from the catheter.

After eliminating various factors, we tried to withdraw water from the catheter balloon, refill it with 30ml of sterile water, and then slowly and uniformly pump back 15ml.

Indwelling catheterization is a common clinical care technique to relieve urinary difficulties, urinary incontinence, urinary retention and to monitor urine output.

In elderly patients, due to degenerative changes in their organs, it is easy for urine to leak out of the side of the catheter after the catheter is left in place, either in a quiet state or with a full bladder, without clamping or after clamping.

Catheter leakage brings greater inconvenience to treatment and care, and also intensifies the patient's pain.
The causes of indwelling urinary catheter leakage are complex and tricky to manage.

The amount of water required for catheter balloon injection is routinely 10 to 15 ml, but considering the problem of urine leakage, clinical nurses will increase the amount of water injection sequentially based on experience, thus there are reports of water injection ranging from 10 to 30 ml.

In fact, the more the amount of water injected into the balloon is not the better, but the key is whether the water balloon can form a uniform sphere after water injection and play a closed role.

For this reason, the in vitro experiments were conducted on the water injection of air bladder, and it was found that when the water injection was 10~15m1, the air bladder was basically "bi-spherical" deformed, and when the water injection reached 30ml, the air bladder showed a uniform round sphere all around, and then slowly and uniformly pumping back the liquid, it was found that the sphere slowly shrank with the reduction of water, but it still maintained a uniform sphere until the pumping back. Until 15ml of liquid is pumped back, the balloon still maintains a good uniform spherical state.

The possible reasons for the analysis are: when injecting 10-15ml of liquid, the internal pressure of the balloon is not large enough to make the balloon completely open and form a "partial spherical" deformity, and when injecting 30ml of liquid, the balloon is completely open and spherical.

When the balloon is completely opened, then slowly and uniformly pump back the liquid, because at this time the internal pressure and tension of the balloon decreases uniformly, the balloon still maintains a uniform spherical state. If the leakage occurs due to the deformation of the balloon of the catheter injection, this method of "water injection and then pumping back" can effectively solve the problem of leakage.